Basics

• What can the positive charge of any nucleus be subdivided into?

  A whole number of smaller particles, each having the same amount of positive charge (protons)
• What did James Chadwick's work provide evidence for?

  The existence of neutrons within the nucleus
• What is the atomic number?

  The number of protons in an atom of an element
• Do all atoms of a particular element have the same number of protons?

  Yes, they do
• How do atoms of different elements differ?

  They have different numbers of protons
• What is the relative charge of a proton?

  +1
• What is the relative charge of a neutron?

  0
• What is the relative charge of an electron?

  • -1
• What is the overall charge of an atom?

  0
• What does it mean when the number of protons equals the number of electrons in an atom?

  The atom has an overall charge of 0
• What is the approximate radius of an atom?

  About 0.1 nm
• How does the radius of a nucleus compare to that of an atom?

  The radius of a nucleus is less than 1/10,000 of that of the atom
• What is the mass number of an atom?

  The sum of the protons and neutrons in an atom
• What are isotopes?

  Atoms of the same element with different numbers of neutrons
• How is relative atomic mass defined?

  An average value that takes into account the abundance of the isotopes of the element
• What are atoms considered in terms of substances?

  Atoms make up all substances and are the smallest part of an element that can exist
• What do chemical symbols represent?

  An atom of an element
• How are compounds formed?

  By elements through chemical reactions
• What do chemical reactions involve when forming compounds?

  The formation of one or more new substances and often involve an energy change
• What do compounds contain?

  Two or more elements chemically combined in fixed proportions
• How can compounds be represented?

  By formulae using the symbols of the atoms from which they were formed
• What is the formula for hydrochloric acid?

  HCl
• How can compounds be separated into elements?

  Only by chemical reactions
• What is a mixture?

  A combination of two or more elements or compounds not chemically combined
• How do the chemical properties of substances in a mixture compare to those in a compound?

  The chemical properties of each substance in the mixture remain unchanged
• How can mixtures be separated?

  By filtration, crystallisation, simple distillation, fractional distillation, and chromatography
• What type of processes are used to separate mixtures?

  Physical processes
• What was the first thought about the structure of atoms?

  Atoms were thought to be tiny spheres that could not be divided
• What model was proposed after the discovery of the electron?

  The plum pudding model
• What did the alpha particle scattering experiment conclude about the atom?

  The mass of an atom was concentrated at the center (nucleus) and that the nucleus was charged
• What was the setup of the alpha particle scattering experiment?

  A beam of alpha particles was aimed at very thin gold foil
• What happened to some alpha particles during the scattering experiment?

  Some emerged from the foil at different angles, and some even came straight back
• Why were the positively charged alpha particles repelled and deflected?

  Because of a small concentration of positive charge in the atom (nucleus)
• Who suggested that electrons orbit the nucleus at specific distances?

  Neil Bohr
• How can the relative atomic mass of carbon be calculated given carbon-14 with 20% abundance and carbon-12 with 80% abundance?

  By using the formula: $((14 \times 20) +$$(12 \times 80)) \div 100 =$$12.4$
• What do electrons occupy in an atom?

  The lowest available energy levels (the shells closest to the central nucleus)
• What does the electronic structure of an atom tell you?

  How many electrons are in each shell
• What is the electronic structure of sodium?

  2, 8, 1
• What are the key components of the atomic model development?

  • Initially thought to be indivisible spheres
  • Plum pudding model after electron discovery
  • Alpha particle scattering showed nucleus concentration
  • Bohr's model suggested electrons orbit at specific distances